I just found a way to avoid the annoying error message being displayed each time PowerDVD 12 is started after the (annoying) unwanted processes and services are disabled:
The "unwanted" processes exe files just has to be removed/renamed. For information regarding which files should be renamed, see http://forum.cyberlink.com/forum/posts/list/23102.page
After removing/renaming these files, PowerDVD won't complain anymore.
Note: each time PowerDVD is updated, the renaming/removing has to be done again.
Cheers!